The present invention relates to compact discs and more particularly relates to an apparatus and method of reconditioning both audio and compact discs by removing scratches and blemishes in the protective plastic layer on one side of the disc which occur through use and handling of the discs.
Compact discs (CD""s)are widely used for storing both audio and visual information in digital form. Compact discs are discs which consist of a disc of plastic having a thickness of about 1 mm to 1.5 mm and typically have a diameter of about 4xc2xe inches. Other types of discs such as digital videodiscs (DVD""s) have a smaller digital information band. The information, in digital form, is recorded on an information layer which consists of a continuous spiral data track. After the data is placed on the disc, a metallic film is placed over the data and it is sealed with a protective layer. Damage to the information layer can occur if scratches or other surface blemishes occur in the plastic protective layer. CD""s generally have a data track on one side while some discs, such as DVDs, store data on both sides.
Reading of discs is accomplished by a laser beam which scans the disc through the plastic protective layer. The laser is reflected by the metallic film. Damage, as mentioned, to the protective layer will interfere with the scanning process such that tracking errors or distortion will occur when the disc is played.
Even relatively small scratches or blemishes resulting from handling of the disc can lead to disturbances in faulty reproduction. The laser reading beam scans the data track and blemishes, imperfections and scratches in the protective layer which is generally a polycarbonate, will hinder the laser""s ability to properly read the data and xe2x80x9cskipsxe2x80x9d will occur.
The prior art discloses various methods and apparatus for refinishing CD""s.
U.S. Pat. No. 5,220,754 shows a method for restoring compact discs in which the disc is held and a scraping action is applied to the coating on the disc.
U.S. Pat. No. 5,571,041 discloses a method for repairing and refinishing audio and video CD""s. The top side of the disc is placed against a soft, covered wheel and secured to the wheel. The disc is spun on low rpm and a heavy cut cleaner applied across the surface of the bottom side of the disc using a clean cotton cloth or pad. This step is repeated at higher rpm using a medium cut cleaner and then a finer cut cleaner. Clear plastic cleaner and a clear plastic polish are then applied using a cotton pad.
U.S. Pat. No. 5,207,759 discloses a method for texturing a disc using a slurry. The slurry includes different sized particles, preferably a first in the 3 micron size range and a second in the 1 micron size range. Particles are used to abrade the surface of the disc. A pad is moved relative to the disc to scour the substrate.
U.S. Pat. No. 5,167,096 discloses a method and apparatus for texturing a substrate. A texturing pad and the disc are rotated about parallel, offset axis and pressed against one another in the presence of a particle slurry. The inner, less compressible region of the pad produces a deeper grooved texturing on an inner, annular surface of the disc.
U.S. Pat. No. 5,099,618 discloses a method for repairing damaged recording discs by removing a part of the protective layer in directions cutting across the data track path.
U.S. Pat. No. 4,179,852 relates to a method and apparatus for polishing a floppy disc. The floppy disc is placed on a circular, resilient pad disposed on a first spindle-mounted circular platen. A circular, fibrous or abrasive polishing disc is disposed on a second spindle-mounted circular platen. The radius of the polishing disc is greater than the width of an annular region to be polished on the disc so that the relative velocities between points on the polishing disc and the points on the floppy disc are uniform. In the apparatus of this patent, the floppy disc and polishing disc are rotated in the same angular direction at first and second velocities.
The present invention relates to a method and apparatus for reconditioning compact discs by removing blemishes or scratches in the polycarbonate or plastic protective layer by a multiple step process in which the discs are first resurfaced and then subsequently polished to their original factory condition.
Re-surfacing is first accomplished in an apparatus having a cabinet in which is mounted a pair of motors having spindles or shafts vertically extending in spaced parallel relationship. The spindles or shafts are rotated in opposite directions, one being rotated clockwise and the other being rotated counter-clockwise. The shafts extend upwardly into a re-surfacing chamber in the cabinet. Each of the shafts extend through a fixed protective sleeve. An arbor is secured to the end of one of the shafts and a resilient foam pad is detachably secured to the arbor by an adhesive or a loop and hook fastener material such as that sold under the trademark Velcro(copyright). A circular pad having an abrasive surface is secured to the upper surface of the foam pad with the abrasive surface facing upwardly. The adjacent, oppositely rotating shaft has a protective sleeve about it and has a threaded upper end. A collar and hub are adjustable and secured to the shaft. The disc to be processed is placed on the collar and a locking knob may be tightened about the threaded distal end of the shaft to secure the disc in place for processing. The collar may be axially adjusted on the shaft to insure that the disc and the abrasive surface are parallel and in full light engagement. A plate-like bearing member may be interposed between the locking knob and the disc. When the disc is positioned for re-surfacing, the plastic protective layer on the underside of the disc overlaps the abrasive material on the pad on the adjacent shaft. The diameter of the arbor and associated abrasive disc are selected so that the abrasive disc does not overlap the annular data track or mirror band the center of the disc being processed.
A water reservoir is provided in the cabinet of the re-surfacing machine and water or other fluid is discharged onto the upper surface of the abrasive material in a wet sanding operation. The motors when energized rotate at a predetermined speed and re-surfacing progresses until the deeper scratches are removed. Abrasive materials having different grits, as for example 30 micron, 15 micron, 9 micron and 3 micron particle size grit, may be progressively used to remove scratches by removing a portion of the plastic protective layer. The water and any removed material is collected in a sump in the bottom of the re-surfacing chamber and discharged to a collection area or drain.
Once re-surfacing has occurred the discs are subjected to a second process which is a polishing process to smooth the protective plastic surface of the disc to its original condition. This is accomplished in an apparatus also having a cabinet containing a pair of spaced-apart motors with vertically extending shafts. The polishing machine is constructed similar to the re-surfacing apparatus described above, having an arbor on one motor shaft which rotates in one direction. A foam pad is detachably securable to the arbor. The compact disc to be processed is mounted on the adjacent shaft at a collar overlapping the foam pad. A locking knob and bearing plate secure the CD in place. The locking knob is in threaded engagement with threads on the upper or distal end of the rotating shaft. Generally, an abrasive material is not utilized in the polishing operation. Instead, a polishing compound, preferably a water based compound, is applied to the upper surface of a foam polishing pad when the motors are energized, polishing continuing until the protective surface of the compact disc is restored to its original condition.
The re-surfacing and polishing operation may be carried out in a single device incorporating the apparatus described above. Also, multiple work stations may be provided in both the re-surfacing and polishing apparatus.